Well... The 900 LEDs are already soldered actually huehuehue x)It's a prototype anyway. I'll just have to cut some connections, and wire the corresponding LEDs to 16 MAX chips.

So generally speaking, I understand it's always better to divide large matrixes into small ones in order to control the whole more quickly.

No, a 30x30 is perfectly workable. eg. If you want 100Hz refresh you need to update at 3kHz. An Arduino can probably do that.

The problem is that it requires constant CPU attention and you want to do other stuff at the same time (a game). You might be able to do it (I haven't done the math for how many CPU cycles it would use) but some MAX2719s will make life much simpler.

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)